1. Field of the Invention
The present invention relates to a device which incorporates floating electrodes and is adapted to measure electrostatic fields. More particularly, the present invention relates to a device for measuring electrostatic fields, such as those present during thunderstorms. The preferred device incorporates the use of floating electrodes.
2. Description of Related Art
Electrostatic fields are measured in many industrial processes and are also measured in several types of research where DC voltages are applied or electrostatic fields are necessary. Presently, devices available for measuring electrostatic fields are rotating voltmeters or radioactive probes. These rotating voltmeters and radioactive probes are both expensive and require constant maintenance. Thus, what is needed is a relatively inexpensive device that is simple to use and requires little maintenance. The device should be able to measure electrostatic fields in industrial processes, the technology lab or during adverse weather conditions to help predict lightning strikes.
It is not unusual to have insulated conducting objects located close to the conductors of a lightning protection system. However, the separation of these objects from the lightning protection system could vary from a few millimeters to some centimeters. When the system is exposed to thunderstorm electric fields, discharge could be initiated between the lightning protection system and the floating conductive body. The critical field for the initiation of corona currents from a floating electrode, when a negative DC voltage is applied to the main gap electrodes, is detected by the discharge of the floating electrode to the earth electrode.
Several studies have examined the influence of a floating body on the breakdown voltage between a high voltage electrode and earth when the floating body is introduced between them. The reduction in the breakdown voltage and the increment in the time to breakdown caused by a floating electrode located approximately 1 mm from the earthed electrode have been investigated under the application of a negative impulse voltage in previous works. Furthermore, the reduction in the breakdown voltage caused by a floating body situated at about one-third of the gap distance from the earthed electrode was investigated by several authors under the application of a positive polarity impulse. The results were summarized in the CIGRE report of 1990. The influence of floating electrode corona sources on the observed reduction in the breakdown voltage of the complex gap was studied by Phillpott et al.